In pipeline pigging operations, it is necessary to periodically replace cups on a pigging mandrel. A pigging mandrel is an elongate body used to support two or more cups. The cups are equipped with a laterally extending central portion, having a peripheral lip around the edge, the lip sealing against the pipe. As the pig is forced through the pipeline, the lip on the cup holds a seal so that pressure fluid behind the mandrel pig forces the entire assembly along the pipe, and accomplishes the necessary pigging action to clean the pipe. Wear is localized at the lip on the replaceable cups. As wear occurs, fluid bypass begins to occur, thereby reducing the cleaning effect of the pig. It also slows down the rate of travel as additional fluid is bypassed. There is a chance that the lip will wear partially, thereby settling toward the bottom of the pipe and distributing the wear on the lip of the cup unevenly around the periphery. As these problems occur, they are cumulative. One cure is to reinforce the lip of the cup. For instance, U.S. Pat. No. 4,365,379 shows a mandrel type pipe with a plurality of cups thereon wherein the cups are flared outwardly by the backing plates adjacent to the cups. An alternate form of reinforcing the lip of the cup is to include reinforcing gussets on the back face of the cup just beneath the lip. This is shown in the patent of Kidd, U.S. Pat. No. 3,480,984. Various and sundry reinforcing or stiffening plates are known.
An alternate approach is to place more resilient material in the lip. However, doubling the thickness of the lip does not necessarily produce twice the life in the pig. In instances, it may simply make the lip stiffer and therefore subject to faster wear. Another reference of interest is U.S. Pat. No. 4,077,079 which shows an abrasion material placed on a bullet-shaped pig body. Various and sundry abrading materials are known including tungsten carbide particles applied in mixed particle sizes either in strips or entirely across the face of elongate bullet-shaped pigs. When placed in strips spiraling around the pig body, they impart twist or rotation to cause the pig to spin as it travels the pipeline, thereby distributing wear around the full surface of the pig. As will be understood, bullet-shaped pig bodies do not use replacement cups, and when worn, the entire pig must be disgarded.
By contrast with the foregoing, a submerged stiffening member integrally cast in the peripheral lip of the replacement cup is set forth in this disclosure as a means of providing longer life in replacement cups. The replacement cup is reinforced by a stiffening member. The preferred form of the stiffening member must be slightly flexible or bendable before casting. It is preferably placed in the mold at the time of casting the replacement cup. Some degree of stiffening is obtained by merely placing the stiffening member in the mold, even should it be located so that it is not near or at the surface of the finished pig cup. The preferred form of stiffening is formed of multiple layers, typically between two and five layers, of heavy cloth of ducking. They are formed together in a strip so that the strip can be cut to length, enabling the proper length to be coiled in the mold before casting. The ducking supports uniformly and regularly positioned staples having staple points. This material is often available in the textile industry and is used in that industry as carding cloth. It has been discovered that the replacement cup of this disclosure can be markedly enhanced in its performance (referring to the number of miles of pipe that can be cleaned by a particular cup before the cup must be disgarded) and gains of perhaps 100% or 200% are not uncommon in contrast with replacement cups not constructed in the mode of this disclosure.
As will be understood on review of the disclosed embodiment, the strip of carding cloth is positioned in the mold at the time of integrally casting the replacement cup. After the unset plastic material has been placed in the mold, the final product which is formed is a replacement cup having a peripheral lip wherein the lip is reinforced by the circular reinforcing member. Thus, if the pipeline has a 24 inch diameter, the replacement cup will have a nominal 24 inch size equipped with a surrounding lip of about 3 or 4 inches in width and a thickness of about 1/2 to 1 inch in thickness. On the inside of that lip, and integrally constructed with it, the reinforcing member is located, then holding the lip stiff somewhat in the fashion of a hoop or reinforcing bead in the lip.
One feature of the present disclosure is the incorporation of a stiffening hoop in the replacement cup lip. The reinforcing hoop enables the cup to yield during operation, but yielding is not so severe as to distort the lip and thereby prevent leakage past the pig during cleaning operation. The abrading surface is reinforced at or in the near vicinity of the tips of the staples which are carried in the carding cloth. Those staples are submerged beneath the surface of the cup lip, thereby forming a part of the body of the cup.
In the preferred embodiment, the peripheral lip has an internally cast hoop like member which stiffens it, and further includes a multitude of staple legs extending radially outwardly of the completed lip. The staple legs define an abrasion surface cooperative with the elastomeric material used in fabrication of the cup thereby obtaining longer life as an abrasion surface. As will be understood from this cursory summary and in greater detail on explanation below, the replacement cup thus has a stiffer lip able to last longer in operation.